The Spectrally Resolved Lyman-Alpha Emission Of Three Lyman-Alpha-Selected Field Galaxies At Z Similar To 2.4 From The HETDEX Pilot Survey

Access full-text files




Chonis, Taylor S.
Blanc, Guillermo A.
Hill, Gary J.
Adams, Joshua J.
Finkelstein, Steven L.
Gebhardt, Karl
Kollmeier, Juna A.
Ciardullo, Robin
Drory, Niv
Gronwall, Caryl

Journal Title

Journal ISSN

Volume Title



We present new results on the spectrally resolved Ly alpha emission of three Ly alpha-emitting field galaxies at z similar to 2.4 with high Lya equivalent width (> 100 angstrom) and Lya luminosity (similar to 10(43) erg s(-1)). At 120 km s(-1) (FWHM) spectral resolution, the prominent double-peaked Lya profile straddles the systemic velocity, where the velocity zero point is determined from spectroscopy of the galaxies' rest-frame optical nebular emission lines. The average velocity offset from systemic of the stronger redshifted emission component for our sample is 176 km s(-1) while the average total separation between the redshifted and main blueshifted emission components is 380 km s(-1). These measurements are a factor of similar to 2 smaller than for UV-continuum-selected galaxies that show Lya in emission with lower Lya equivalent widths. We compare our Lya spectra to the predicted line profiles of a spherical "expanding shell" Ly alpha radiative transfer grid that models large-scale galaxy outflows. Specifically, blueward of the systemic velocity where two galaxies show a weak, highly blueshifted (by similar to 1000 km s(-1)) tertiary emission peak, the model line profiles are a relatively poor representation of the observed spectra. Since the neutral gas column density has a dominant influence over the shape of the Lya line profile, we caution against equating the observed Lya velocity offset with a physical outflow velocity, especially at lower spectral resolution where the unresolved Lya velocity offset is a convoluted function of several degenerate parameters. Referring to rest-frame ultraviolet and optical Hubble Space Telescope imaging, we find that galaxy-galaxy interactions may play an important role in inducing a starburst that results in copious Lya emission as well as perturbing the gas distribution and velocity field, both of which have strong influence over the Lya emission line profile.



LCSH Subject Headings


Chonis, Taylor S., Guillermo A. Blanc, Gary J. Hill, Joshua J. Adams, Steven L. Finkelstein, Karl Gebhardt, Juna A. Kollmeier et al. "The Spectrally Resolved Lyman-alpha Emission of Three Lyman-alpha Selected Field Galaxies at z~ 2.4 from the HETDEX Pilot Survey." arXiv preprint arXiv:1308.1957 (2013).